System and method for synchronizing engine and transmission system operation within an agricultural vehicle

ABSTRACT

A system and method for controlling a transmission system is provided. One agricultural vehicle includes a vehicle controller configured to instruct an engine controller to maintain an engine at a constant speed and to receive a first signal from a transmission controller indicative of gear shift initiation. The vehicle controller is also configured to instruct the engine controller to maintain the engine at a current torque upon receipt of the first signal and to receive a second signal from the transmission controller indicative of gear shift completion. The vehicle controller is configured to instruct the engine controller to maintain the engine at the constant speed upon receipt of the second signal.

BACKGROUND

The invention relates generally to agricultural vehicles and, moreparticularly, to a system and method for synchronizing engine andtransmission system operation within an agricultural vehicle.

Various types of agricultural vehicles (e.g., tractors, floaters,applicators, sprayers, etc.) are employed to deliver fertilizer,pesticides, herbicides, seeds, or other products to the surface of afield and/or to perform other agricultural functions (e.g., harvesting,cultivating, etc.). Typical agricultural vehicles include an engineconfigured to power the vehicle, and a transmission system configured totransfer engine power to rotating wheels at a desired gear ratio.Certain agricultural vehicles employ an automatic transmissionconfigured to automatically shift gear ratios based on engine load,engine speed and/or ground speed, among other factors.

Certain agricultural vehicles include a cruise control system configuredto maintain a constant vehicle speed by continuously regulating enginespeed. For example, certain cruise control systems may maintain theengine at a desired speed (e.g., approximately 2100 rotations per minute(RPM)) to achieve a desired vehicle speed. During a gear shift, theratio of engine speed to ground speed changes. Because the ground speedremains substantially constant, the engine speed is varied to facilitategear shifting. However, many modem engines are effective at maintaininga constant engine speed when the cruise control system is engaged.Unfortunately, maintaining a constant engine speed while thetransmission is shifting gears may interfere with the shifting process.

BRIEF DESCRIPTION

In one embodiment, an agricultural vehicle includes a vehicle controllerconfigured to instruct an engine controller to maintain an engine at aconstant speed and to receive a first signal from a transmissioncontroller indicative of gear shift initiation. The vehicle controlleris also configured to instruct the engine controller to maintain theengine at a current torque upon receipt of the first signal and toreceive a second signal from the transmission controller indicative ofgear shift completion. The vehicle controller is configured to instructthe engine controller to maintain the engine at the constant speed uponreceipt of the second signal.

In another embodiment, a method for synchronizing engine andtransmission system operation within an agricultural vehicle includesinstructing an engine controller to maintain an engine at a constantspeed and receiving a first signal from a transmission controllerindicative of gear shift initiation. The method also includesinstructing the engine controller to maintain the engine at a currenttorque upon receipt of the first signal and receiving a second signalfrom the transmission controller indicative of gear shift completion.The method includes instructing the engine controller to maintain theengine at the constant speed upon receipt of the second signal.

In another embodiment, a vehicle includes a transmission systemconfigured to change gear ratios and a transmission controllercommunicatively coupled to the transmission system, and configured tocontrol operation of the transmission system. The agricultural vehiclealso includes an engine coupled to the transmission system andconfigured to transfer torque to the transmission system, and an enginecontroller communicatively coupled to the engine, and configured tocontrol the operation of the engine. The agricultural vehicle includes avehicle controller communicatively coupled to the transmissioncontroller and to the engine controller. The vehicle controller isconfigured to instruct the engine controller to maintain the engine at aconstant speed and to receive a first signal from the transmissioncontroller indicative of gear shift initiation. The vehicle controlleris also configured to instruct the engine controller to maintain theengine at a current torque upon receipt of the first signal and toreceive a second signal from the transmission controller indicative ofgear shift completion. The vehicle controller is configured to instructthe engine controller to maintain the engine at the constant speed uponreceipt of the second signal.

DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 is a perspective view of an embodiment of an agricultural vehiclethat may employ a control system configured to synchronize engine andtransmission system operation;

FIG. 2 is a schematic diagram of an embodiment of a control system thatmay be employed within the agricultural vehicle of FIG. 1;

FIG. 3 is an exemplary graph of control parameters versus time for atransmission up shift;

FIG. 4 is an exemplary graph of control parameters versus time for atransmission down shift; and

FIG. 5 is an embodiment of a method for synchronizing engine andtransmission system operation.

DETAILED DESCRIPTION

FIG. 1 is a perspective view of an embodiment of an agricultural vehicle10 that employs a control system 12 configured to synchronize engine andtransmission system operation. The agricultural vehicle 10 includes atank 14 where material, such as fertilizer, pesticide, herbicide and/orother products, are stored for distribution to a field. As illustrated,the vehicle 10 also includes a frame 16, a cab 18, and a hood 20. Theframe 16 provides structural support for the cab 18, the hood 20, andthe tank 14. Furthermore, the cab 18 provides an enclosed space for anoperator, and the hood 20 houses the engine and/or other systemsconfigured to facilitate operation of the vehicle 10. The agriculturalvehicle 10 also includes wheels 22 configured to support the frame 16,and to facilitate movement of the vehicle across the field.

As discussed in detail below, the engine is coupled to a transmissionsystem configured to transfer torque from the engine to the wheels 22.In the present embodiment, the transmission system includes an automatictransmission configured to automatically shift gear ratios based onengine load, engine speed and/or ground speed, among other factors. Theengine and transmission system are communicatively coupled to thecontrol system 12, which may include various controllers and/or userinterfaces configured to control operation of the engine andtransmission system. For example, the control system 12 may include atransmission controller, an engine controller, and a vehicle controller.However, it should be appreciated that the engine control functionality,the transmission control functionality and/or the vehicle controlfunctionality may be performed by a single controller in certainembodiments. The transmission control system 12 controls the operationand communication between various systems, such as between thetransmission controller and the transmission system, or between theengine controller and the engine. As such, the transmission controlsystem 12 enables the automatic transmission system of the floater 10 toshift gears, such as when the floater 10 is being operated via enginecruise control.

In certain embodiments, a vehicle controller may be configured toinstruct an engine controller to maintain an engine at a constant speedexcept during a gear shifting process. During the gear shifting process,the vehicle controller may be configured to instruct the enginecontroller to maintain the engine at a current torque. To facilitatecontrol timing, the vehicle controller receives signals from atransmission controller indicating initiation and termination of thegear shifting process. In such an embodiment, the temporary transitionfrom the constant speed to the constant torque during the gear shiftingprocess enables the transmission system to effectively change gears,thereby facilitating up shifts and/or down shifts. While the illustratedagricultural vehicle 10 is a floater, it should be appreciated thatalternative vehicles, such as tractors, sprayers, and/or any type ofvehicle, including agricultural and non-agricultural vehicles, mayemploy the control system 12 to synchronize operation of the engine andtransmission system.

FIG. 2 is a schematic diagram 40 of an embodiment of a control system 12that may be employed within the agricultural vehicle 10 of FIG. 1. Asillustrated, the control system 12 includes a vehicle controller 42, atransmission controller 44, and an engine controller 46. As will beappreciated, the controllers 42, 44, and 46 may each include one or moreprocessors, memory devices, and/or storage devices. Furthermore, thecontrollers 42, 44, and 46 are communicatively coupled to one anothervia a communication bus, such as the illustrated CAN bus 48. In thisconfiguration, the controllers 42, 44, and 46 function cooperatively tocontrol operation of the engine and transmission system. In theillustrated embodiment, the controllers 42, 44 and 46 arecommunicatively coupled to a user interface 50 via the CAN bus 48. Theuser interface 50 enables an operator to provide input to the vehiclecontroller 42. For example, the user interface 50 may enable an operatorto activate the cruise control, select an engine speed and/or adjustvarious parameters associated with engine/transmission system operation.Consequently, the user interface 50 may include various input controlsand/or a display for presenting information to the operator. In certainembodiments, the controllers 42, 44, and 46, and the user interface 50may be communicatively coupled to one another by any suitable wired orwireless communication system.

As illustrated, the transmission controller 44 is communicativelycoupled to a transmission system 52, and configured to control operationof the transmission system 52. For example, the transmission controller44 may instruct the transmission system 52 to shift gears (e.g., upshift or down shift) based on engine load, engine speed and/or groundspeed, among other factors. Alternatively, the transmission controller44 may monitor gear shifts automatically performed by the transmissionsystem 52. In certain embodiments, the transmission system 52 includesan automatic transmission configured to automatically change gear ratiosas the agricultural vehicle 10 traverses a field. For example, incertain embodiments, the automatic transmission may be a transmissionmanufactured by Allison Transmission, Inc. of Indianapolis, Ind.However, it should be appreciated that any suitable transmission may beutilized within the transmission system 52 in alternative embodiments.

Furthermore, the engine controller 46 is communicatively coupled to anengine 54, and configured to control operation of the engine 54. Forexample, the engine controller 46 may be configured to continuouslyregulate engine speed such that the engine 54 maintains a constant RPM.Alternatively, the engine controller 46 may be configured tocontinuously regulate engine torque such that the engine 54 maintains aconstant torque. As will be appreciated, the engine 54 may be anysuitable device (e.g., a diesel engine) configured to transfer torque tothe transmission system 52. For example, in certain embodiments, theengine may be manufactured by Fiat Powertrain Technologies of Orbassano,Italy. In the illustrated embodiment, the engine 54 is coupled to thetransmission system 52, and configured to transfer torque to thetransmission system 52, thereby driving the wheels 22 to rotate.

During operation, the control system 12 will synchronize engine andtransmission system operation to facilitate gear shifting while aconstant RPM cruise control is activated. First, an operator mayactivate a constant RPM cruise control via the user interface 50. Thevehicle controller 42 will then instruct the engine controller 46 tomaintain the engine 54 at a constant RPM, such as between about 1800 toabout 2300 RPM (e.g., based on the operator selection via the userinterface 50). By way of example, the vehicle controller 42 will send acommand to the engine controller to maintain the engine speed atapproximately 2100 RPM. The engine controller 46 will then regulateengine speed to achieve the desired constant RPM.

When the transmission controller 44 determines that a gear shift isdesired (e.g., during acceleration, deceleration, elevation change,etc.), the transmission controller 44 will instruct the transmissionsystem 52 to shift gears (e.g., up shift or down shift). Thetransmission controller 44 will also send a signal to the vehiclecontroller 42 indicative of gear shift initiation. Once the vehiclecontroller 42 receives the signal indicative of gear shift initiation,the vehicle controller 42 will instruct the engine controller 46 tomaintain the current torque (i.e., transition from a constant RPM cruiseto a constant torque cruise). Consequently, the engine controller 46will regulate engine torque to maintain the level present when theengine controller 46 received the instructions to enter the constanttorque cruise. For example, if the engine torque was 85 percent of thetotal torque capacity when the engine controller 46 received theinstructions from the vehicle controller 42, the engine controller 46will maintain a torque of 85 percent of the total capacity, regardlessof RPM.

Once the gear shift is complete, the transmission controller 44 willsend a signal to the vehicle controller 42 indicative of gear shiftcompletion. Upon receipt of the signal, the vehicle controller 42 willinstruct the engine controller 46 to maintain the engine 54 at theoriginally desired constant speed (i.e., return to the constant RPMcruise). The temporary transition from the constant RPM cruise to theconstant torque cruise during the gear shifting process enables thetransmission system to effectively change gears without engineinterference, thereby facilitating smooth up shifts and/or down shifts.

FIG. 3 is an exemplary graph 60 of control parameters versus time for atransmission up shift. As illustrated, curve 62 represents a signal fromthe transmission controller 44 indicating that a gear shift is inprogress. Specifically, segment 64 of curve 62 corresponds to gear shiftinitiation, and segment 66 of curve 62 corresponds to gear shifttermination. Consequently, the duration 68 between gear shift initiationand gear shift termination represents the total time associated withshifting gears. For example, the shift duration 68 may be approximately1.0 to 2.0 seconds. In certain embodiments, the shift duration 68 may beapproximately 1.3 seconds. Curve 70 represents the current gear. Asillustrated, a first segment 72 of curve 70 corresponds to a first gearat the start of the gear shift process, and a second segment 74 of curve70 corresponds to a second gear at the end of the gear shift process.Segment 76 is representative of a transition between the first gear andthe second gear, and illustrates a positive gear change (i.e., an upshift). For example, segment 72 may be representative of gear number 2,and segment 74 may be representative of gear number 3. However, itshould be appreciated that the gear transition may be between any twoconsecutive gears within the transmission system.

Curve 78 represents engine speed as a function of time. As illustrated,the engine speed initially increases as the engine controller 46 raisesengine RPM to reach a desired level. However, when the vehiclecontroller 42 receives a signal indicative of gear shift initiation (ata time corresponding to segment 64), the vehicle controller 42 instructsthe engine controller 46 to maintain a constant torque rather than aconstant RPM. While in the constant torque cruise, the engine speedincreases to a local maxima 80, and then decreases to a local minima 82before rising again. As will be appreciated, the decrease in enginespeed is induced by the change in gear ratios. Once the gear shiftingprocess is complete (at a time corresponding to segment 66), the vehiclecontroller 42 will instruct the engine controller 46 to return to theconstant RPM cruise. Thus, by changing from engine speed control totorque control during the gear shifting process, the transmission systemcan effectively change gears without engine interference, therebyfacilitating smooth up shifts.

Curve 84 represents a rotation speed of a transmission output shaft. Incertain embodiments, the transmission output shaft is coupled to thevehicle wheels by one or more differentials and/or drive shafts. Asillustrated, the transmission output shaft speed steadily increasesbefore, during, and after the gear shift, with a temporary sharpincrease at location 86. Thus, the ground speed of the vehicle steadilyincreases throughout the gear shifting process.

FIG. 4 is an exemplary graph 90 of control parameters versus time for atransmission down shift. As illustrated, curve 92 represents a signalfrom the transmission controller 44 that a gear shift is in progress.Specifically, segment 94 of curve 92 corresponds to gear shiftinitiation, and segment 96 of curve 92 corresponds to gear shifttermination. Consequently, the duration 98 between gear shift initiationand gear shift termination represents the total time associated withshifting gears. For example, the shift duration 98 may be approximately1.0 to 2.0 seconds. In certain embodiments, the shift duration 98 may beapproximately 1.1 seconds. Curve 100 represents the current gear. Asillustrated, a first segment 102 of curve 70 corresponds to a first gearat the start of the gear shift process, and a second segment 104 ofcurve 100 corresponds to a second gear at the end of the gear shiftprocess. Segment 106 is representative of a transition between the firstgear and the second gear, and illustrates a negative gear change (i.e.,a down shift). For example, segment 102 may be representative of gearnumber 5, and segment 104 may be representative of gear number 4.However, it should be appreciated that the gear transition may bebetween any two consecutive gears within the transmission system.

Curve 108 represents engine speed as a function of time. As illustrated,the engine speed initially decreases as the agricultural vehicle slowsdown, such as when the vehicle is under load and being lugged down.However, when the vehicle controller 42 receives a signal indicative ofgear shift initiation (at a time corresponding to segment 94), thevehicle controller 42 instructs the engine controller 46 to maintain aconstant torque rather than a constant RPM. While in the constant torquecruise, the engine speed decreases to a local minima 110, and thenincreases to a local maxima 112 before decreasing again. As will beappreciated, the increase in engine speed is induced by the change ingear ratios. Once the gear shifting process is complete (at a timecorresponding to segment 96), the vehicle controller 42 will instructthe engine controller 46 to return to the constant RPM cruise. Thus, bychanging from engine speed control to torque control during the gearshifting process, the transmission system can effectively change gearswithout engine interference, thereby facilitating smooth down shifts.

Curve 114 represents a rotation speed of a transmission output shaft. Incertain embodiments, the transmission output shaft is coupled to thevehicle wheels by one or more differentials and/or drive shafts. Asillustrated, the transmission output shaft speed steadily decreasesbefore, during, and after the gear shift, with some oscillations atlocations 116. Thus, the ground speed of the vehicle steadily decreasesthroughout the gear shifting process.

FIG. 5 is an embodiment of a method 120 for synchronizing engine andtransmission system operation. At step 122, a vehicle control systemdetermines whether constant RPM cruise control is activated. Forexample, to activate the cruise control, an operator may select adesired engine speed via a user interface. If the cruise control isactivated, a vehicle controller instructs an engine controller tomaintain an engine at the selected constant speed (i.e., RPM), at step124. For example, the vehicle controller may instruct the enginecontroller to maintain the engine at approximately 1800 to 2300 RPM. Byway of example, the vehicle controller may instruct the enginecontroller to maintain the engine at approximately 2100 RPM. In certainembodiments, the constant engine speed may be a peak operating RPM ofthe engine. Next, at step 126, the engine controller receives theinstructions from the vehicle controller and adjusts the engine speed.Then, at step 128, the engine maintains the desired constant speed.

At step 130, the control system determines whether a gear shift isinitiated. In certain embodiments, the gear shift may be an up shift, ora down shift. However, in other embodiments, the control system may onlyproceed to step 132 when a down shift is initiated. If a gear shiftinitiated, the transmission controller sends a signal indicative of gearshift initiation to the vehicle controller, at step 132. Next, at step134, the vehicle controller receives the signal indicative of gear shiftinitiation. Then, at step 136, the vehicle controller instructs theengine controller to maintain the current engine torque (i.e., theengine torque present when the instructions are received). For example,the vehicle controller may instruct the engine controller to maintainthe current engine torque, such as a torque from 0 to 100 percent ofengine capacity.

At step 138, the engine controller receives the instructions from thevehicle controller and controls the engine to maintain the desiredconstant torque. Next, at step 140, the engine maintains the desiredconstant torque. Then, at step 142, the control system determineswhether the gear shift is complete. When the gear shift is complete, atstep 144, the transmission controller sends a signal indicative of gearshift completion to the vehicle controller. Once complete, the method120 returns to step 124 and performs steps 124 through 128. The method120 maintains the engine at the desired constant speed per step 128until another gear shift is initiated.

The temporary transition from the constant RPM cruise to the constanttorque cruise during the gear shifting process enables the transmissionsystem to effectively change gears without engine interference, therebyfacilitating smooth up shifts and/or down shifts. As will beappreciated, fewer or more steps may be part of the method 120 forsynchronizing engine and transmission system operation. Furthermore, incertain embodiments, the steps may be performed in a different orderthan described above. Likewise, in other embodiments, the functions ofthe vehicle controller, engine controller, and/or transmissioncontroller may be performed by fewer or more than three controllers. Inaddition, the steps of method 120 may be performed using software,hardware, or a combination of software and hardware.

While only certain features of the invention have been illustrated anddescribed herein, many modifications and changes will occur to thoseskilled in the art. It is, therefore, to be understood that the appendedclaims are intended to cover all such modifications and changes as fallwithin the true spirit of the invention.

The invention claimed is:
 1. An agricultural vehicle comprising: avehicle controller that during operation instructs an engine controllerto maintain an engine at a constant speed, receives a first signal froma transmission controller indicative of gear shift initiation, instructsthe engine controller to maintain the engine at a current torque uponreceipt of the first signal, receives a second signal from thetransmission controller indicative of gear shift completion, andinstructs the engine controller to maintain the engine at the constantspeed upon receipt of the second signal.
 2. The vehicle of claim 1,wherein the constant speed comprises a peak operating speed.
 3. Thevehicle of claim 1, wherein the transmission controller during operationsends the first signal upon initiation of an up shift.
 4. The vehicle ofclaim 1, wherein the transmission controller during operation sends thefirst signal upon initiation of a down shift.
 5. The vehicle of claim 1,wherein the transmission controller is communicatively coupled to atransmission system.
 6. The vehicle of claim 5, wherein the transmissionsystem comprises an automatic transmission.
 7. The vehicle of claim 1,wherein the vehicle controller, the engine controller and thetransmission controller are communicatively coupled to one another.
 8. Avehicle comprising: a transmission system that changes gear ratiosduring operation; a transmission controller communicatively coupled tothe transmission system, wherein the transmission controller controlsoperation of the transmission system during operation; an engine coupledto the transmission system, wherein the engine transfers torque to thetransmission system during operation; an engine controllercommunicatively coupled to the engine, wherein the engine controllercontrols the operation of the engine during operation; and a vehiclecontroller communicatively coupled to the transmission controller and tothe engine controller, wherein the vehicle controller during operationinstructs the engine controller to maintain the engine at a constantspeed, receives a first signal from the transmission controllerindicative of gear shift initiation, instructs the engine controller tomaintain the engine at a current torque upon receipt of the firstsignal, receives a second signal from the transmission controllerindicative of gear shift completion, and instructs the engine controllerto maintain the engine at the constant speed upon receipt of the secondsignal.
 9. The vehicle of claim 8, wherein the transmission systemcomprises an automatic transmission that during operation automaticallychanges gear.
 10. The vehicle of claim 8, wherein the engine duringoperation operates at a constant speed.
 11. The vehicle of claim 8,wherein the transmission controller, the engine controller, and thevehicle controller are communicatively coupled to one another.
 12. Thevehicle of claim 8, comprising a user interface communicatively coupledto the vehicle controller.
 13. The vehicle of claim 8, wherein theconstant speed comprises a peak operating speed.
 14. The vehicle ofclaim 8, wherein the transmission controller during operation sends thefirst signal upon initiation of a down shift.